The present invention relates to a system for an actuator for controlling engine idling speed for a vehicle, and more particularly to a system which is provided with a device for preventing the malfunction of the engine when the actuator does not work.
Heretofore, a closed loop feedback control system has been provided for controlling the idling speed to a desired idling speed by adjusting the amount of air or the amount of the air-fuel mixture to be induced in the engine in dependency on the error signal which is the difference between a desired reference idling speed and the detected idling speed.
On the other hand, it occasionally happens that the engine runs on even if the ignition switch is turned off. In order to prevent the running on of the engine operation, there has been proposed a system using an actuator in the above described automatic idling speed control system. The actuator comprises a motor and an axially movable rod driven by the motor. In the system, the throttle valve follows the retraction of the rod of the actuator to close the induction passage of the engine. When the ignition switch is turned off, the rod of the actuator is further retracted, so that the throttle valve rotates from the idling open position to a further closed position to stop the engine running.
In such a system, if the actuator does not work by an accident, such as solidification of oil in the actuator which may occur when the vehicle is parked for a long time in the cold, the throttle valve is positioned at the closed position in the subsequent engine idling operation. Therefore, the engine is not properly operated in the idling state.